1. Field
The disclosure relates to a method, system, and article of manufacture for the writing of data of a first block size in a Redundant Array of Independent Disks (RAID) array that stores and mirrors data in a second block size.
2. Background
Redundant Array of Independent Disks (RAID) is a category of disk drives that combine two or more disk drives to provide fault tolerance for data. RAID allows for the redundant storage of the same data across a plurality of disks. In certain configurations of RAID, such as RAID-10 data may be mirrored to recover from a failure of a disk. The physical disks of a RAID may be said to be in a RAID array that may be addressed by an operating system as one single disk. Data may be written in stripes in a RAID array, wherein data striping is the spreading out of blocks of each file across a plurality of disk drives.
RAID-10 provides high availability by combining features of RAID-0 and RAID-1. RAID-0 increases performance by striping volume data across multiple disk drives. RAID-1 provides disk mirroring which duplicates data between two disk drives. By combining the features of RAID-0 and RAID-1, RAID-10 provides a second optimization for fault tolerance. RAID-10 may provide data mirroring from one disk drive module (DDM) to another DDM. RAID 10 stripes data across half of the disk drives in the RAID-10 configuration. The other half of the array mirrors the first set of disk drives. Access to data is preserved if one disk in each mirrored pair remains available.
In some cases, RAID-10 offers faster data reads and writes than RAID configurations such as RAID 5 because RAID-10 does not need to manage parity. However, with half of the DDMs in the group used for data and the other half used to mirror that data, RAID-10 disk groups may not use storage space very efficiently.
A sector is a specifically sized division of a disk. Previously, one sector of a disk was generally configured to hold 512 bytes of information. However, recently certain disks are being configured to hold 4096 bytes (i.e., 4 Kilobyte) of information by disk manufacturers.
A block is a group of sectors of a disk that an operating system can address. Count-key-data (CKD) is a disk data organization model of certain operating systems in which the disk is assumed to be comprised of a fixed number of tracks, each having a maximum data capacity. Multiple records of varying length may be written on each track of a CKD disk, and the usable capacity of each track depends on the number of records written to the track. CKD architecture derives its name from the record format, which comprises a field containing the number of bytes of data and a record address, an optional key field, and the data itself. CKD records are stored in 512 byte blocks.